本文将比较中助动词的补出这一GMAT语法知识点分享给大家，希望对大家备考GMAT考试有所帮助。
助动词的补出都出现在主语比较中，为了避免比较上的歧义。
补出的助动词：be/ do/ did/ have/ 情态动词
具体补出什么，取决于than/as前面句子的动词——be补be，实意动词补do/did/does，完成时态补have/ had/ has，情态动词补情态动词。
注意：
主谓结构或主系表结构，主语比较一般是不需要补出助动词的，但是补出了也不一定错。但是，如果than/as后面事态发生变化，一定要补出助动词！
一个比较特殊的题：
2-96 There are hopeful signs that we are shifting away from our heavy reliance on fossil fuels: more than ten times as much energy is generated through wind power now than it was in 1990.
(A) generated through wind power now than it was
(B) generated through wind power now as it was
(C) generated through wind power now as was the case
(D) now generated through wind power as it was
(E) now generated through wind power than was the case
key: C
这个题目因为时态的转变必须补出was；其次比较对象是整句话的属性，而不仅仅是energy，所以不用that来补出，但是却又不能用it来指代主语，所以就只能用as was the case了。
总之，关于比较和比较中的省略，说难也不难。
上述就是GMAT语法知识点中比较中助动词的补出介绍，希望可以给大家参考。
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